Definition: In this task, you are given an input list A. You need to convert all the alphabets in the list with a number representing their position in the English alphabet. E.g., replace A by 1, B by 2, a by 1, b by 2, and so on.
Input: ['4793', 'B', '6455', 'a', 'R', '6987']

4793, 2, 6455, 1, 18, 6987